Freq of PI coil

[Unregistered]

Hi All
Just a curious question
What would be the design frequency of PI coil be .. rough figure ... its resonant Frequency
should have Hi Q or Low Q ..
thank
George

[porkluvr]

Ideally, a "perfect" PI coil's resonant frequency would be infinite because we try to eliminate capacitance in the cable and in the coil windings. Of course we cannot eliminate, only minimize.

Read bbsailor's fast mono coil article

here: http://www.geotech1.com/pages/metdet...s/FastCoil.pdf

To measure Q you must have a test frequency. LCR meters would have a sine wave test frequency that has no comparison to the pulse output from a PI machine.

But since we generally try to minimize the PI coil's winding resistance, I guess that's shooting for hi-Q.

[Unregistered]

Yes I read his artcle but He did not say ideal freq. And am understanding that is good to have low Q for heavey mineral soil.. so is good to have High Q coil for low mineral soil and Low Q for Heavey ?????
And seem to me like freq will vary from 400khz to around 1mhz ????
thankyou again
george

[Carl-NC]

There is no ideal frequency. You want it as high as possible, but practically anything above 400-500kHz should be plenty fast enough. For a critically damped coil Q=2.

- Carl

[porkluvr]

For a critically damped coil Q=2.

- Carl

I hope the R used to figure "Q" includes the damping resistor? Yes?

[Carl-NC]

yup.

[Unregistered]

Ok I had better add that to calculation
thanks you